Question: Solve: $\dfrac{3}{5} + \dfrac{7}{10} - \dfrac{1}{2} = $
Let's look at the multiples of each denominator and see which multiples they have in common. Denominator Multiples ${5}$ $5, \underline{{10}}, 15, 20$ ${10}$ $\underline{{10}}, 20, 30$ ${2}$ $2, 4, 6, 8, \underline{{10}}$ The least common multiple is ${10}$. Let's use multiplication to make each fraction have a denominator of $10$. $\begin{aligned} &{\dfrac{3}{5}}=\dfrac{{3} \times 2}{{5} \times 2} = {\dfrac{6}{10}}\\\\ &{\dfrac{7}{10}}\\\\ &{\dfrac{1}{2}}=\dfrac{{1} \times 5}{{2} \times 5} = {\dfrac{5}{10}} \end{aligned}$ $\begin{aligned} &{\dfrac{3}{5}} + {\dfrac{7}{10}} - {\dfrac{1}{2}}\\\\ =& {\dfrac{6}{10}} + {\dfrac{7}{10}} - {\dfrac{5}{10}}\\\\ =&\dfrac{6 + {7} - {5}}{10}\\\\ =&\dfrac{13 - 5}{10}\\\\ =&\dfrac{8}{10} \end{aligned}$ $\dfrac35 + \dfrac{7}{20} - \dfrac{1}{2} = \dfrac{8}{10}$ $\dfrac8{10}$ can also be written as $\dfrac45$.